1. Field of the Invention
The present invention relates to the acquisition of very small liquid samples of precisely identical volume and, particularly, to optically analyzing such minute samples. This invention is also directed to sampling apparatus for repetitively acquiring very small liquid samples of the same volume and, especially, to sampling devices in which an optical measurement may be performed. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
There are many use environments, the fields of medical research and pharmaceutical development being examples, where it is necessary to accurately acquire fluid samples with volumes which may be as small as a few nanoliters. In these same fields, it is also often desired to measure optical characteristics of the acquired fluid samples. Such optical characteristics may, again by way of example, comprise light absorption, fluorescence or Raman spectra.
It has, in the prior art, been difficult to repetitively acquire very small fluid samples of identical volume and subsequently deliver such samples, without loss, into position for analysis. This difficulty may, to a large degree, be attributed to the fact that the prior art procedures have involved at least one transfer step. Thus, by way of example, it has previously been necessary to "hand-off" the collected sample from the sampling device to the analysis instrument. Additionally, the nature of the previously available sampling devices has rendered it difficult to ensure that each of a plurality of repetitively collected samples would be of identical volume, i.e., the prior art has typically required performance of a quantitative measurement on the collected samples, and this, in turn, has imposed a relatively high tolerance range on the collected sample volume.